Coordination cationic polymerization

According to Eliel s definition, the cationic coordinated polymerization of the cis and trans isomers of l-chloro-2-isobutoxy-... 

In their polymerization, many individual alkene molecules combine to give a high molecular weight product Among the methods for alkene polymerization cationic polymerization coordination polymerization and free radical polymerization are the most important An example of cationic polymerization is... 

Polyethylene (Section 6 21) A polymer of ethylene Polymer (Section 6 21) Large molecule formed by the repeti tive combination of many smaller molecules (monomers) Polymerase chain reaction (Section 28 16) A laboratory method for making multiple copies of DNA Polymerization (Section 6 21) Process by which a polymer is prepared The principal processes include free radical cationic coordination and condensation polymerization Polypeptide (Section 27 1) A polymer made up of many (more than eight to ten) amino acid residues Polypropylene (Section 6 21) A polymer of propene Polysaccharide (Sections 25 1 and 25 15) A carbohydrate that yields many monosacchande units on hydrolysis Potential energy (Section 2 18) The energy a system has ex elusive of Its kinetic energy... 

Epichlorohydrin Elastomers without AGE. Polymerization on a commercial scale is done as either a solution or slurry process at 40—130°C in an aromatic, ahphatic, or ether solvent. Typical solvents are toluene, benzene, heptane, and diethyl ether. Trialkylaluniinum-water and triaLkylaluminum—water—acetylacetone catalysts are employed. A cationic, coordination mechanism is proposed for chain propagation. The product is isolated by steam coagulation. Polymerization is done as a continuous process in which the solvent, catalyst, and monomer are fed to a back-mixed reactor. Pinal product composition of ECH—EO is determined by careful control of the unreacted, or background, monomer in the reactor. In the manufacture of copolymers, the relative reactivity ratios must be considered. The reactivity ratio of EO to ECH has been estimated to be approximately 7 (35—37). 

In Section 6.21 we listed three main methods for polymerizing alkenes cationic, free-radical, and coordination polymerization. In Section 7.15 we extended our knowledge of polymers to their stereochemical aspects by noting that although free-radical polymerization of propene gives atactic polypropylene, coordination polymerization produces a stereoregulai polymer with superior physical properties. Because the catalysts responsible for coordination polymerization ar e organometallic compounds, we aie now in a position to examine coordination polymerization in more detail, especially with respect to how the catalyst works. 

Polymerization (Section 6.21) Process by which a polymer is prepared. The principal processes include free-radical, cationic, coordination, and condensation polymerization. 

One of the major advantages of radical polymerization over most other forms of polymerization, (anionic, cationic, coordination) is that statistical copolymers can be prepared from a very wide range of monomer types that can contain various unprotected functionalities. Radical copolymerization and the factors that influence copolymer structure have been discussed in Chapter 7. Copolymerization of macromonomers by NMP, ATRP and RAFT is discussed in Section 9.10.1. 

The general subject of lactone polymerization has been reviewed (7, 19). Polymerization of e-caprolactone can be effected by at least four different mechanisms categorized as anionic, cationic, coordination, and radical. Each method has unique attributes, providing... 

Chain gro tvth polymerization begins when a reactive species and a monomer react to form an active site. There are four principal mechanisms of chain growth polymerization free radical, anionic, cationic, and coordination polymerization. The names of the first three refer to the chemical nature of the active group at the growing end of the monomer. The last type, coordination polymerization, encompasses reactions in which polymers are manufactured in the presence of a catalyst. Coordination polymerization may occur via a free radical, anionic, or cationic reaction. The catalyst acts to increase the speed of the reaction and to provide improved control of the process. 

Why is it possible to manufacture polystyrene by radical, anionic, cationic and coordination polymerization methods ... 

First, new "living" initiators have been discovered (although not always as efficient), which respond to other mechanisms, i.e. cationic (5) or even radical ones (6), and can accordingly accomodate other types of monomers. A recent typical example is the coordination polymerization of butadiene by bis (n3-allyl-trifluoro-acetato-nickel) to yield a "living" pure 1.4 cis-poly-butadienyl-nickel, able to initiate in turn the polymerization of monomers like isoprene or styrene (7). 

The first attempts at ROP have been mainly based on anionic and cationic processes [4,5]. In most cases, polyesters of low molecular weight were recovered and no control on the polymerization course was reported due to the occurrence of side intra- and intermolecular transesterification reactions responsible for a mixture of linear and cyclic molecules. In addition, aliphatic polyesters have been prepared by free radical, active hydrogen, zwitterionic, and coordination polymerization as summarized in Table 2. The mechanistic considerations of the above-mentioned processes are outside the scope of this work and have been extensively discussed in a recent review by some of us [2 ]. In addition, the enzyme-catalyzed ROP of (di)lactones in organic media has recently been reported however, even though this new polymerization procedure appears very promising, no real control of the polyesters chains, or rather oligomers, has been observed so far [6]. 

Isomerization polymerizations can be associated with coordination catalyst systems, ionic catalyst systems, and free radical systems. The cationic isomerization polymerization of 4-methyl-1-pentene is of interest because the product can be viewed as an alternating copolymer of ethylene and isobutylene. This structure cannot be obtained by conventional... 

A very broad range of initiators and catalysts are reported in the scientific literature to polymerize lactones. The polymerization mechanisms can be roughly divided into five categories, i.e., anionic polymerization, coordination polymerization, cationic polymerization, organocatalytic polymerization, and enzymatic polymerization. 

The ionic chain polymerization of unsaturated linkages is considered in this chapter, primarily the polymerization of the carbon-carbon double bond by cationic and anionic initiators (Secs. 5-2 and 5-3). The last part of the chapter considers the polymerization of other unsaturated linkages. Polymerizations initiated by coordination and metal oxide initiators are usually also ionic in nature. These are called coordination polymerizations and are considered separately in Chap. 8. Ionic polymerizations of cyclic monomers is discussed in Chap. 7. The polymerization of conjugated dienes is considered in Chap. 8. Cyclopolymerization of nonconjugated dienes is discussed in Chap. 6. 

Kinetics of Addition Polymerization. As the name suggests, addition polymerizations proceed by the addition of many monomer units to a single active center on the growing polymer chain. Though there are many types of active centers, and thus many types of addition polymerizations, such as anionic, cationic, and coordination polymerizations, the most common active center is a radical, usually formed at... 

Stereochemistry3 13 Of Polymerization At -78°C Of 2-(2-Pyridy1)-Propene As A Function of Cation and Cation Coordination... 

On the basis of the nature of the initiation step, polymerization reactions of unsaturated hydrocarbons can be classified as cationic, anionic, and free-radical polymerization. Ziegler-Natta or coordination polymerization, though, which may be considered as an anionic polymerization, usually is treated separately. The further steps of the polymerization process (propagation, chain transfer, termination) similarly are characteristic of each type of polymerization. Since most unsaturated hydrocarbons capable of polymerization are of the structure of CH2=CHR, vinyl polymerization as a general term is often used. 

Conjugated dienes (1,3-butadiene, isoprene) have suitable nucleophilicity to undergo cationic polymerization. There is, however, not much practical interest in these processes since the polymers formed are inferior to those produced by other (free-radical, coordination) polymerizations. A significant characteristic of these polymers is the considerably less than theoretical unsaturation due to cyclization processes.132 A fully cyclized product of isoprene has been synthesized163 by constant potential electrolysis in CH2C12. 

Using some of these catalysts, coordination polymerization of ethylene at high rate were performed in water. A highly branched polymer was obtained with cationic Pd diimio complex, whereas a neutral Ni complex with a sulfonate group afforded a linear polymer.592... 

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